As is well known to the entire world, in the last two years superconductor research has undergone a revolution principally based upon the discovery by Nobel laureates J. G. Bednorz and K. A. Mueller that oxidic-type superconductors exist which have critical temperatures (Tc) above about 45.degree. K. During 1987 and in 1988 to date, researchers around the world have reported on various oxide compositions which reportedly have Tc's ranging up to 273.degree. K. and beyond. While, as applicants' understand it at the time of the present writing, claims of very high Tc's for oxidic-type superconductors are based upon detections of the Meissner effect which have been ephemeral and non-repeatable, it is intended that the scope of this application not be limited to any particular oxidic compound or any particular oxidic system so long as the material in question has use in the superconducting field.
A quick survey of the recent technical literature through Chemical Abstracts has indicated that the following oxidic materials including compounds, phases, mixtures, doped materials, etc. have been proposed for superconducting use:
YBa.sub.2 Cu.sub.3 O.sub.7-x PA1 MBa.sub.2 Cu.sub.3 O.sub.7 M=Nd, Dy, Er, Tm or mixtures PA1 MBa.sub.2 Cu.sub.3 O.sub.6 M=Sa, Ho PA1 La.sub.2-x Sn.sub.x CuO.sub.4 PA1 La.sub.2 CuO.sub.4 doped with fluorine PA1 YBa.sub.2 Cu.sub.3 O.sub.6.8 doped with fluorine PA1 EuBa.sub.2 Cu.sub.3 O.sub.9-x PA1 EuBa.sub.2 (Cu.sub.1-y M.sub.y).sub.3 O.sub.9-x M=Cr, Mn, Fe, Co, Ni or Zn PA1 GdBaCu.sub.3 O.sub.7-x PA1 Ba.sub.2 SmCu.sub.3 O.sub.9-x PA1 InSnO.sub.2 PA1 La.sub.2-x M.sub.x CuO.sub.4 PA1 La.sub.2-x Sr.sub.x CuO.sub.4 PA1 Ba.sub.2 YCu.sub.3 O.sub.9-y PA1 GdBa.sub.2 Cu.sub.3 O.sub.7-x PA1 YBa.sub.2 (Cu.sub.1-x Fe.sub.x).sub.3 O.sub.7-y PA1 (Y.sub.1.2 Ba.sub.0.8).sub.4 Cu.sub.4 O.sub.16-x PA1 YBa.sub.3 Cu.sub.3 O.sub.y F.sub.x PA1 Y.sub.3-x Ba.sub.x Cu.sub.2 O.sub.7-y PA1 Bi-Sr-Cu-O system PA1 La.sub.3-x Ba.sub.3-x Cu.sub.6 O.sub.14-y PA1 YBa.sub.2 Cu.sub.3 O.sub.7-x S.sub.y PA1 EuBa.sub.2 Cu.sub.3 O.sub.x PA1 YBa.sub.2 Cu.sub.3 O.sub.9-y PA1 La.sub.1.85 Sr.sub.0.15 CuO.sub.4 PA1 Ba.sub.2 RCu.sub.3 O.sub.x R=Gd, Ho, Er or Dy PA1 YBa.sub.2 (Cu.sub.1-x Ag.sub.x).sub.3 O.sub.7-y PA1 YBa.sub.2 (CuO.sub.0.94 FeO.sub.0.06).sub.3 O.sub.9-y PA1 YBa.sub.2 Ag.sub.3 O.sub.x PA1 La.sub.2 CuO.sub.4-y PA1 Dy.sub.x Ba.sub.1-x CuO.sub.3-y PA1 Molybdenum Oxides and Bronzes - Alkali Molybdenum Bronze PA1 (Y, Ho)Ba.sub.2 Cu.sub.3 O.sub.7 PA1 Nb, Si, Al oxides Japanese Pat. Appln. No. 87-170,108 PA1 Ge, Al, Nb oxides Japanese Pat. Appln. No. 87-171,924 PA1 BaPb.sub.1-x Bi.sub.x O.sub.3 PA1 Nb/Al/Al.sub.2 O.sub.3 PA1 Nb/Ge-Al-O PA1 Pb, Bi, In oxides ##EQU1##
Those acquainted with the art will appreciate that the foregoing list of oxidic superconductors (or more accurately materials suggested for superconductor use) is not exhaustive and is increasing on a day-to-day basis. For example, on page 36 of the April 1988 edition of Scientific American a new superconductor is reported as composed of bismuth, strontium, calcium, copper and oxygen. The superconductor reportedly having a Tc as high as 84.degree. K. apparently can also contain aluminum. Those persons will also appreciate that where exact compositions are listed, in reality any element in the composition may be present in a sub- or super-stoichiometrical amount and may be limited to or substituted in whole or in part with a particular isotope of the element in question such as O.sup.18, Gd.sup.155, etc. The superconductor composition may also be doped with metals, metalloids and non-metals. Each and all of these variations and others are contemplated within the term "oxidic superconducting materials" as employed in this specification and claims. Currently, known ways of preparing such oxidic superconducting materials are disclosed in the review by M. Hirabayashi in Nippon Kinzoku Gakkai Kaiho 1987, 26(10), pages 943-949, Chemical Abstract Reference 108-66605f. Reference is also made to the paper "Synthesis of a Superconducting Oxide by Oxidation of a Metallic Precursor", Yurek et al, Metallurgical Transactions A, Vol. 18A, October 1987, pp. 1813-1817, the brief communication "Direct Synthesis of a Metal/Superconducting Oxide Composite by Oxidation of a Metallic Precursor", Yurek et al, JAECS, October 1987, pp. 2635-2636 and the paper "Superconducting Microcomposites by Oxidation of Metallic Precursors, Yurek et al, Journal of Metals, January 1988, pp. 1614 18. Those skilled in the art appreciate that oxidic super-conductors are essentially ceramic-like materials which are not readily formable into desirable product configurations such as wire, tape, coils, etc. The purpose of the present invention is to provide an improved method of making oxidic superconductors starting with a metallic superconductor precursor.